As you say, this value only appeared in Hadoop 2.4.0:

http://hadoop.apache.org/docs/r2.4.0/api/org/apache/hadoop/yarn/api/ApplicationConstants.html
http://hadoop.apache.org/docs/r2.3.0/api/org/apache/hadoop/yarn/api/ApplicationConstants.html

File.pathSeparator should already be ":" vs ";", which is what you intend right?
http://docs.oracle.com/javase/7/docs/api/java/io/File.html#pathSeparator

I'm missing what this changes then. I understand that the char may vary on the client vs cluster, and that's why it's right to reference a symbolic constant, but these seem to be the same in that respect.